Blast furnace charging apparatus pressurization



Jan. 10, 1967 A, M H JR 3,297,432

BLAST FURNACE CHARGING APPARATUS PRESSURIZATION Filed Dec. 26, 1963 V RELIEF GAS LINE GAS ELEEDER l CLEANER y F AND COOLER Inventor ALBERT MOHRJR.

United States Patent 3,297,432 BLAST FURNACE CHARGING APPARATUS PRESSURIZATION Albert Mohr, Jr., Chicago, Ill., assignor to John Mohr & Sons, Chicago, 11]., a corporation of Illinois Filed Dec. 26, 1963, Ser. No. 333,539 4 Claims. (Cl. 75-41) The present invention relates to blast furnaces and more particularly it relates to improved pressurization means for blast furnace charging apparatus to increase the effective lift of the apparatus and thereby improve the operating cycle of the furnace.

Utilization of high air flow and higher operating temperatures in blast furnaces in recent years has brought about significant productivity increases in blast furnace operation. Such operating practices have gained wide acceptance. Use of high air flow, however, has required an increase in the top furnace pressure in the area adjacent the charging apparatus of the furnace. Partially to accommodate for the high top furnace pressure and still maintain continuity of operation the multiple chamber charging apparatus was introduced.

One such multiple bell charging system includes three separate bells and defines two chambers. The lowermost bell of a three bell system defines a movable separation between the top area of the blast furnace and the lower chamber of the charging apparatus. An intermediate bell defines a movable separation between the lower chamber and the upper chamber of the charging apparatus, and, the uppermost bell defines the upper movable wall of the upper chamber and separates it from the atmosphere. The two chamber-three bell system illustrated herein, defines an air lock wherein the blast furnace may be charged on a continuous cycling basis. It can readily be appreciated that without an air lock such as provided with charging apparatus of the above type the material laden furnace gases spill into the atmosphere during charging of each furnace burden to the furnace.

Due to increased furnace operating pressure in present furnace practice it is essential also to pressurize the chamber of the charging apparatus during operation of the furnace. One practice is to pressurize the lower chamber of the charging apparatus at a pressure higher than the top furnace pressure to assure that if a leak occurs past the lowermost bell of the charging apparatus gas will flow from the higher pressure lower chamber to the top furnace area. The lower chamber may be pressurized with a cleaned blast furnace gas.

The theory of pressurization of the lower chamber of the charging apparatus with cleaned gas at a pressure higher than top furnace pressure is that if a leak occurs past the lowermost bell then clean gas will flow from the lower chamber to the top furnace area and the higher pressure in the lower chamber will prevent escape of the heavily abrasive materials laden gases in the top furnace area to the lower chamber. It can readily be seen that if a high velocity flow of abrasive materials laden gas is passed over the leaking surface progressive deterioration of the leak surfaces will occur with the result that the effective life of the equipment will be shortened. However, if a clean gas is passed over the leak surfaces then there is nothing to cause injury to the leak surfaces. In theory this application is most attractive. In practice, however, the initially clean gases quickly become laden with abrasive particles which are in suspension in the lower chamber. Further, if a leak occurs the high pressure gas in the lower chamber will pass along through the material to reach the area of leakage. In movement of the gas at high velocity to the leak area it will pick up particles, hold them in suspension in the moving stream and pass through the leak area as an abrasive material laden gas that may carry as many or more abrasive particles as the raw blast furnace gas coming off of the top of the furnace. To'this extent there may be no measurable gain in pressurizing the chambers with cleaned gases at pressures higher than the top furnace pressure. Further, in order to pressurize the chambers to a pressure level higher than blast furnace top pressures it is necessary to employ a gas compressor to bring the gases to the desired pressure level.

In addition, present pressurization systems do not allow for a rapid change in furnace top pressure. It has been found that the charges on the lowermost and intermediate bells coacting with the pressurizing pressures in the lower and upper chambers respectively are of sufficient magnitude to force these bells open thereby damaging the charging apparatus.

The present invention contemplates the provision of an improved pressurization system for blast furnace charging apparatus. Pressurization of gases is eliminated at any stage of processing and a compressor is not required thus eliminating a troublesome and expensive portion of the apparatus. The present invention involves pressurization of the lower chamber of a three-bell charging apparatus, for example, with raw blast furnace gases. A direct gas connection is made between the top furnace area of the blast furnace up-take pipe and the lower chamber to provide for pressure equalization between these two areas. The upper chamber of the two chamber system is pressurized in two stages. The chamber first is pressurized with a cleaned blast furnace gas. This gas is taken from the top furnace area and passed through a cleaner filter to remove suspended particles from the gas. In cleaning the gases they are passed through a suitable filtering medium to trap the suspended and abrasive particles carried along from the top furnace area of the blast furnace. In so cleaning the gases the velocity is reduced, energy is dissipated, and the gas pressure level reduced to a level slightly below the top furnace pressure level (generally 2 p.s.i.g. below top furnace pressure level). The cleaned gas then is passed through a conduit and into the upper chamber when said chamber is to be pressurized. The upper chamber of the charging apparatus first is pressurized with the cleaned gases, then said chamber is connected directly to the top furnace area and the chamber pressure between the two areas is equalized. In this manner the volume of raw blast furnace gas introduced into the upper chamber is considerably less than if the chamber were pressurized completely with raw blast furnace gas. The resultant gas charge in the upper chamber contains suspended particles but to a much less extent than would otherwise occur.

It, accordingly, is a general object of the present invention to provide an improved pressurization system for blast furnace charging apparatus.

An additional object of the present invention resides in the provision of an improved pressurization system for blast furnace charging apparatus wherein the chambers of the charging apparatus are pressurized to the same level as the top furnace area.

A further object of the present invention resides in the provision of an improved pressurization system that avoids auxiliary compression of the gases employed for pressurization.

Another object of the present system resides in the provision of an improved pressurization system for blast furnace charging apparatus employing blast furnace waste gases for the complete pressurization thereof.

Still another object of the present invention resides in the provision of an improved pressurization means for a three bell charging apparatus wherein the pressure level in the lower chamber is equalized with the top furnace pressure during one portion of the cycle and wherein the upper chamber of the charging apparatus is pressurized totop furnace pressure level in a two stage pressurization system to a pressure level equal with the top furnace pressure level.

An additional object of the present invention resides in the provision of an improved pressurization means for pressurizing the upper chamber of a three bel blast furnace charging apparatus wherein the upper chamber first is pressurized with clean gas to a level below top furnace pressure level and then is pressurized with blast furnace gas at top furnace pressure to equalize the pressure level in the upper chamber with the top furnace pressure level.

A further objective of the present invention resides in the provision of an improved pressurization means for a three bell charging apparatus wherein the pressure level in the upper chamber is changed instantaneously to prevent a forced opening of the intermediate bell should furnace top pressure change rapidly.

Still another object of the present invention resides in the provision of an improved pressurization means for blast furnace charging apparatus that is economical to install and use, that is durable in use, and that permits extended equipment life.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

Figure l is a schematic representation of the application of the pressurization system of the present invention to a three bell-two chamber charging apparatus for a blast furnace; and

Figure 2 is a fragmentary, enlarged, partly sectioned view of the bell operating rods taken along lines 2-2 of Figure 1.

It has long been known that it is desirable to pressurize the charging chambers of a blast furnace charging apparatus to prolong the life of the equipment, specifically, of the movable members and the seats for said members. It can readily be understood that if a leak occurs between a moveable bell and the mating seat area the pressure will seek to equalize on both sides of the bell and leak area. In a three bell charging apparatus if the lower chamber is at atmospheric pressure, for example, and the top blast furnace area is at operating level somewhat above atmospheric pressure level, then the material laden raw blast furnace gas will flow from the top furnace area into the lower chamber through the leak area until the pressure in both areas is equalized. The flow of gases through the relatively small leak opening may occur at high velocities depending in part upon the pressure differential between the two areas. The material in the blast furnace gas is abrasive in character and will tend to aggravate wear of the bell and bell seat of the leak area, increase the size of the leak area, increase the rate of destruction of the equipment and shorten the useful cycle life of the furnace.

It has been and is the practice to pressurize the chambers of the charging apparatus for blast furnaces at pressure levels higher than the top furnace pressure level. Such pressurization generally is made with clean gases containing a small amount of abrasive particles or other materials. The theory of such pressurization is that in the event a leak does occur such cleaned gases will pass over the leak area and the tendency to aggravate the wear in the leak area will be minimal. As noted above, however, in practice the chambers generally contain many ore, lime, coke or other particles in suspension therein and the cleaned gases are intermixed in this atmosphere immediately upon charging to the chambers. The particles are suspended in the pressurized chamber in much the same manner as in the unpressurized chamber. To this extent the cleansed gases are not clean after charging into the chamber being pressurized. Further, particles are picked up by the moving stream of gases during travel to the leak area so that they are laden with abrasive materials when they pass from the high pressure chamber to the relatively lower pressure top furnace area.

In accord with the present invention it is intended that the upper and lower chambers of the illustrative three bell blast furnace charging apparatus be pressurized with blast furnace gases, the lower chamber being pressurized wholly with such gas and the upper chamber being pressurized in a two-stage operation, first with a cleaned blast furnace gas 'at a pressure level below the top furnace pressure level,

said pressure level of the cleaned gas being a function of the top furnace pressure level diminished by the pres sure loss occuring during removal of materials from. the blast furnace gas stream and second by raw blast furnace gas to bring the upper chamber to a pressure level the same as the top furnace pressure level.

I have discovered that pressurization of the chambers of the charging apparatus is more important than pressuri zation thereof with cleaned gases. The preferred pressure condition for best operation has been noted to be at a stage where the pressure differential between the top furnace area and the upper and lower chambers of the charging apparatus is minimal and preferably zero.

With zero pressure differential between the top furnace area and the lower chamber, for example, there will be no tendency for gas fiow between the two areas in the event that a leak occurs therebetween. If the pressure differential is minimal there will be, at most, a low velocity flow of gases past the leak and between the areas. The low velocity flow is less destructive in nature than that which would occur if a higher pressure differential existed across the lower bell.

As seen in the drawings, the furnace is indicated generally at 10. The top furnace area 12 of the furnace is the area which receives the materials charge from the charging apparatus, indicated generally at 14.

During operation of the blast furnace to produce iron, gases are generated. These gases collect in the top furnace area above the upper surface of the materials and pass into the uptake pipes 16 and 18. The materials charged do not extend fully to the top of the furnace 10 and there is a collection of gases under pressure in the top furnace area 12 immediately adjacent the charging apparatus 14.

Charging apparatus 14 illustrated in the drawings is a three bell charging system having a first or lower chamber 20 closed at the bottom by the lower bell 22 and at the top by the middle bell 24 of the three bell system. The upper chamber 26 of the charging apparatus is closed at the bottom by the middle bell 24 and at the top thereof by the uppermost bell 28. The side walls of the upper and lower chambers are defined by metal skirt portions 30 and 32, respectively. The lower wall portion or chamber 20 is rigidly afiixed to the top furnace structure. The upper chamber 26 and remaining charging apparatus is supported on the structural members of the lower chamber. A materials-receiving hopper 34 is supported above the upper chamber and includes a storage hopper 36 and a 'guide chute 38. A skip car 40 is adapted to carry materials to be charged to the furnace from the ground level along the tracks 42 and to dump them into the guide chute 38 of the materials-receiving apparatus.

The storage hopper 36 may be rotatable so that as each hopper of material from the guide chute 38 is dumped into the storage hopper 36 the hopper 36 rotates to provide means for even distribution of the charge materials within said hopper. In this manner the materials are more thoroughly distributed (leveled) before charging to the blast furnace proper and more uniform distribution of materials will be assured within the furnace for optimum operation during the iron making process.

The operating rods for movement of the bells 22, 24 and 28 of the three bell charging apparatus are mounted one within the other, as seen in the fragmentary view of FIGURE 2. The outermost operating rod 44 is affixed at one end to the upper bell 28 and at the other end to operating means (not shown). The operating rod 46 for the middle bell 24 is telescopically mounted within the outermost rod 44 and is rigidly afiixed at one end to the second bell 24 and at the other end to separate operating means (not shown). The operating rod 48 for the lower bell 22 is telescopically received within the tubular second rod 46 and is rigidly aflixed at one end to the lower bell 22 and at the other end to separate operating means (not shown).

A gas conduit 50 extends from the uptake pipe 18 to conduits 51 and 56. A manually operated normally open valve 80 is interposed in the gas duct 50 between the uptake pipes 18 and conduits 51 and 56 to shut the flow of gases from the uptake pipes to these conduits in emergency.

The gas conduit 50 extends from the uptake pipe 18 through conduit 56 to the chamber 20 of the charging apparatus. A manually or automatically operable valve 52 is interposed in the gas conduit 56 between conduit 50 and the lower chamber 20 to control the flow of gases from the uptake pipe to the lower chamber as desired.

When an automatically operable valve 52 is provided an air, hydraulic or electrical line 52 extends from the valve operator 53 of the valve 52 to a control center C of the system to provide means for remote operation of the valve 52 in an automatic sequence or manually. The gas conduit 50 extends through conduit valves 58 and 60 to a relief line 62. Each of the valves 58 and 60, respectively, is connected through lines 58 and 60 to the control sequence center C of the system.

A second gas conduit 64 extends from the uptake pipe 18 to a gas cleaner 66. The cleaner 66 is adapted to receive the raw blast furnace gases and pass them through a suitable filter medium to remove the suspended particles therefrom. In this manner the gases are cleaned and passed along to a clean gas conduit 68. The conduit 68 extends from the cleaner 66 to a bleeder or relief line 70 through valve 72. The valve 72 is automatically operable and connected through line 72 to the control center C. A feeder line 74 extends from the clean gas conduit 68 through valve 76 and into a common conduit 51 which latter conduit also is connected to the conduit 50 containing the raw blast furnace gases. The valve 76 is automatically operable and is connected through line 76' to the control center C of the system.

The control center C includes means 52", 58", 60", 72" and 76" for manual remote operation of each of the valves connected thereto and means A for automatic sequencing operation of the valves to permit automatic pressurization of the chambers 20 and 26 of the charging apparatus.

Prior systems for pressurization of the chambers of the charging apparatus include compression means for compression of the cleaned gases prior to introduction into the chambers. A compressor compresses the cleaned gases to a pressure level above the top furnace pressure level. Top furnace pressure levels vary during operation and to this extent it is necessary with present pressurization methods either to attempt close control of the top furnace pressure level, vary the pressure of the gases being charged to the chambers of the charging apparatus or feed gases to the chambers of the charging apparatus at a pressure level higher than the highest transient pressure level of the top furnace area.

It has been found that generally when the blast furnace gas is passed through a cleaner a pressure drop of about 2 p'.s.i.g. will occur (depending, of course, in part upon the initial pressure of the gas and the furnace operating practice) so that the cleaned gas will be lower in pressure by about 2 pounds under normal operating conditions as compared to the raw blast furnace gas. Compressors are required in prior practice to bring the gas back to the pressure level of the raw blast furnace gases and above in order to provide a pressure in the chamber higher than the top furnace pressure level. In my method, there is no requirement for pressurization of the cleaned gases. The compressor is eliminated from the system.

During operation of the blast furnace, the pressure in chamber 20 is equalized with the pressure level at the top furnace area, indicated generally at 12 in FIGURE 1. When the pressure in the chamber 20 and the top furnace area 12 are equalized there will be little or no tendency for flow of gases between the two areas notwithstanding the fact that a leak may be present along the sealing area defined between the bell 22 and the mating seating area defined at the lower terminal of the skirt 32 of chamber 20. The bell 22 then is required only to sustain the materials charge within the chamber 20 until ready for dis charge into the furnace proper.

The chamber 26 is pressurized during operation of the apparatus so that when the materials charge is to be dumped from the chamber 26 into chamber 20, in sequence, the pressure diflerential across bell 24 will be minimal. Gravity forces can then act to lower bell 24 when the separate operating system, not shown, holding bell 24 is released. The charge will move undisturbed from chamber 26 into chamber 20. Before the chamber 26 is loaded with materials from the hopper 36, the chamber 26 is depressurized to atmospheric pressure level by opening valve 60 permitting gravity forces to lower bell 28 when the separate operating system, not shown, holding said bell is released. The charge will move undisturbed from hopper 36 to chamber 26. In this manner, the pressure on both sides of the bell 28 being equalized there will be little tendency for material laden gases to flow from the chamber 26 to atmosphere during the charging sequence to load chamber 26, the exchange that does occur being primarily due to varying thermal conditions of the gases.

In present methods of pressurization of the chambers of the charging apparatus attempts are made to continue pressurization of the area generally defined by the lower chamber walls and bell system so that the higher pressure clean gases in this area will tend to keep the material laden blast furnace gases out of this area, thus avoiding contamination of the lower chamber with dirty gas. It can readily be seen that while suitable equipment may be provided to compress cleaned gases during the chamber closed position defined during part of the cycle of operation of the apparatus, when the bell 22 is lowered the pressurization system, in effect, will be attempting to pressurize an infinitely large volume (that volume including the furnace itself). The provision of pressurization equipment sufficient to handle such loads would place an unreasonable operating and economic burden upon the operators thereof and to that extent such equipment is not provided and is not intended for use in this manner.

In the present method of pressurization of the charging apparatus, the valve 52 is opened, manually or by automatic pressure responsive sequencing means. When the valve 52 is open, the lower chamber 20 is directly connected through the uptake pipe 18 to the top furnace area 12. The gas pressure in the top furnace area and in the stack 18 is directed through the conduits 50 and 56 to the closing of valve 76.

7 the chamber 20 and the pressure on both sides of the bell 22 are equalized, there being only transient differentials, which differentials are a function of the transfer rate of pressure changes in one chamber or the other. The valve 52 will normally be open to provide means for continuous pressure equalization between the top furnace area 12 of the furnace and the chamber 20 of the charging apparatus.

Chamber 26 of the charging apparatus is pressurized in a two-step sequence to facilitate reduction in the amount of particles per cubic foot of gas. The raw blast furnace gas first is directed to :a gas cleaner (66 in FIGURE 1) where substantially all of the suspended particles are removed from the gaseous body through suitable filter means such as a water filter, mechanical filter medium, cyclonic precipitator, or the like. Passage of the gases through the cleaner results in a pressure drop across the cleaner due to dissipation of energy in transition of the gases through the resistance passage. It has been found that under normal blast furnace operating conditions, the pressure drop will average about 2 p.s.i.g. The lower pressure cleaned gases then are passed through the conduits 68 and 74, through the now opened valve 76 and into the chamber 26 until the pressure in the chamber 26 is at the same level as the unit pressure in the conduits 68 and 74 feeding the gas to said chamber. At this time, the valve 76 is again closed with valve 60 remaining closed and valve 58 still in closed position. When the gas cleaner is isolated from the chamber, the valve 58 is opened and the raw blast furnace gases pass from the uptake pipe 18, through normally open valve 80 and into common conduit 51 for passage into the chamber 26. The blast furnace gas enters the chamber 26 to equalize the pressure between said chamber and the top furnace area 12. The conduit to the uptake pipe 18 is kept open to assure continued pressure equalization between said chambers, very little gas flow occurring once pressure equalization is achieved.

When the chamber 26 is pressurized to top furnace pressure level, the bell 24 may be opened to drop materials from chamber 26 into chamber 20 in the proper charging sequence, chamber 20 being continuously pressurized to top furnace pressure level through conduit 50 and normally open valve 52. If a leak occurs between the sealing faces of the chambers or between the lower chamber and the top furnace area, there is little or no likelihood of high velocity gas flow through the leak area due to substantial pressure equalization between the areas on either side of the sealing bells.

It has been found that generally when the blast pressure is reduced for the furnace, rapid changes in furnace top pressure can result. If simultaneous depressurization of upper chamber 26 is not accomplished, a forced opening of bell 24 can occur due to the differential pressure existing 'across it co-acting with the burden material on it. This forced opening can damage the operating system, not shown, supporting bell 24 rendering the entire charging apparatus inoperable. In my method chamber 26 is connected to the furnace area 12 by means of uptake pipe 18 and conduits 50 and 51 during the majority of the charging cycle. During the period before valve 58 is opened, the pressure in chamber 26 is not usually of sufficient magnitude to cause a forced opening of bell 24. In some cases furnace top pressures are such that a forced opening of bell 24 can occur prior to the opening of valve 58 and In these cases a pressure sensing device 81iis provided between chambers 20 and 26. Thus constant monitoring of the pressure across bell 24 is pro-' vided. In the event the pressure in chamber 20, essentially the pressure in furnace area 12, changes beyond a predetermined safe limit, valve 60 will reduce the pressure in chamber 26 to the pressure of chamber 20 at which time control of valve 60 will be returned to control center C.

Thus, with my apparatus pressurization of the blast furnace charging apparatus chambers is realized without the requirement for gas compressor equipment and with improved performance in that the pressure equalization on either side of the sealing bells of the charging apparatus avoids high velocity fiow of abrasive materials laden gases from one area to another through a leak area.

During operation of the blast furnace charging apparatus pressurization apparatus and method various valve combinations will be open or closed in accord with the stage of sequential operations. A valve sequence chart is presented below to illustrate more clearly the sequence of valve operations in accord with the method set forth herein.

All Bells Prior to Closedand Opening of Prior to During After Valve (Fig. 1) Chambers Bell 24 Opening Opening Closing 20 and 26 and After Bell 28 Bell 28 0fBell28 Pressurized Closing Bell 24 Closed Closed Closed Closed Open. Open Open Closed Closed-. Closed. Closed Closed Open Closed Closed. Open Open Open Open .r- Open.

While a specific illustration of the present invention is shown and described, it will, of course, be understood that other modifications and alternative procedures may be employed without departing from the true spirit and scope of the invention. It is intended by the appended claims to cover all such modifications and alternative constructions and procedures as fall within their true spirit and scope.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An improved method for blast furnace gas pressurization of a blast furnace having a charging apparatus with a lower chamber and an upper chamber the lower chamber being separated from the top furnace area by a lower movable bell, the upper chamber being separated from the lower chamber by a middle movable bell and from atmosphere by an upper movable bell, said method including the steps of passing raw blast furnace gases from the top furnace area of the blast furnace to the lower chamber to pressurize said lower chamber to top furnace pressure level to equalize pressure levels in the lower chamber and the top furnace area across the lower movable bell; passing raw blast furnace gases through a gas cleaner to remove suspended particles therefrom; and pressurizing said upper chamber to top furnace pressure level to equalize the pressures in the upper chamber, lower chamber and top furnace area across the lower bell and the middle bell, said pressurization of the upper chamber being accomplished in a two step manner wherein first the cleaned blast furnace gas at a pressure level lower than the top furnace pressure level is passed from the gas cleaner to the upper chamber until the upper chamber pressure level is equal to the pressure level of the cleaned gas, and second passing raw blast furnace gases to the upper chamber to pressurize the upper chamber to top furnace pressure level with raw blast furnace material laden gases.

2. An improved method for blast furnace gas pressurization of a blast furnace three bell materials-charging apparatus having a lower chamber separated from the top furnace area by the lower movable bell of the three bell system and an upper chamber separated from the lower chamber by the middle movable bell of the bell system and from atmosphere by the upper movable bell of the bell system, said method including the steps of: equalizing the pressure across the lower bell of the charging system by direct pressure connection between the top furnace area of the blast furnace and the lower chamber of the charging apparatus; passing raw blast furnace gases through a gas cleaner to remove suspended particles therefrom; and pressurizing the upper chamber to top furnace pressure level to equalize the pressures in the upper chamber, lower chamber and top furnace areas across the lower bell and the middle bell, said pressurization of the upper chamber being accomplished by passing the cleaned blast furnace gas at a pressure level lower than the top furnace pressure level from the gas cleaner to the upper chamber until the upper chamber unit pressure level is equal to the unit pressure level of the cleaned gas, isolating the gas cleaner from the upper chamber, and passing raw blast furnace gases to the upper chamber to pressurize the upper chamber to top furnace pressure level with said blast furnace gases.

3. An improved method for blast furnace gas pressurization of a blast furnace three bell materials charging apparatus having a lower chamber separated from the top furnace area by the lower movable bell of the three bell system and an upper chamber separated from the lower chamber by the middle movable bell of the bell system and from atmosphere by the upper movable bell of the bell system, said'method including the steps of: equalizing the pressure across the lower bell of the charging system by direct pressure connection between the top furnace area of the blast furnace and the lower chamber of the charging apparatus and maintaining said pressure equalization during operation of the blast furnace; removing suspended paiticles from the blast furnace gases; and pressurizing the upper chamber of the charging apparatus by passing the cleaned gases into the upper chamher until the upper chamber unit pressure level is equalized with the unit pressure level of the cleaned gas, and pressurizing the upper chamber to top furnace pressure level by direct pressure connection between the top furnace area of the blast furnace and the upper chamber of the charging apparatus.

4. An improved apparatus for pressurization of a blast furnace charging apparatus having a lower chamber and an upper chamber, the lower chamber being separated from the top furnace area by a lower movable bell, the upper chamber being separated from the lower chamber by a middle movable bell and from atmosphere by an upper movable bell, said apparatus including: a first conduit having flow control means therein and extending from the top furnace area to the lower chamber; a second conduit having flow control means therein and extending from the top furnace area to the upper chamber; gas cleansing means; a gas conduit extending to said cleansing means to conduct gases from the top furnace area to said cleansing means; a clean gas conduit having flow control means therein and extending from the gas cleansing means to the upper chamber of the charging apparatus; a pressure relief conduit connected to said lower and upper chambers and having normally closed flow control means therein; a transducer adapted to sense the pressure levels in the upper and lower chambers, to compare them, and to send an output signal to the normally closed flow control means in the pressure relief conduit said output signal being a function of the pressure differential between the upper and lower chambers, the normally closed flow control means being biased to open upon realization of a predetermined pressure differential between said chambers; and sequence control means to control the pressurization of the lower and upper chambers of the charging apparatus in a manner whereby the flow control means in the first conduit is opened and kept open to permit pressure equalization between the top furnace area and the lower chamber, the flow control means in the clean gas conduit is opened and kept open to permit pressure equalization between the pressure level in said clean gas conduit and the upper chamber, said clean gas conduit flow control means being closed when pressure equalization between the upper chamber and the pressure in the clean gas conduit occurs, and opening of the flow control means in the second conduit upon closing of said flow control means in the clean gas conduit to permit pressure equalization of the upper chamber with the top furnace area.

References Cited by the Examiner UNITED STATES PATENTS 2,200,488 5/1940 Clemmitt et al. 26627 2,215,872 9/1940 Fox et al. 26627 2,408,945 10/1946 Mohr et a1. 26627 2,516,190 7/1950 Dougherty et a1. 266-27 X 2,585,800 2/1952 Le Viseur et a1 266-27 X 3,045,996 7/ 1962 Rice 26631 DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, W. TARRING,

Assistant Examiners. 

1. AN IMPROVED METHOD FOR BLAST FURNANCE GAS PRESSURIZATION OF A BLAST FURNACE HAVING A CHARGING APPARATUS WITH A LOWER CHAMBER AND AN UPPER CHAMBER THE LOWER CHAMBER BEING SEPARATED FROM THE TOP FURNACE AREA BY A LOWER MOVABLE BELL, THE UPPER CHAMBER BEING SEPARATED FROM THE LOWER CHAMBER BY A MIDDLE MOVABLE BELL AND FROM ATMOSPHERE BY AN UPPER MOVABLE BELL, SAID METHOD INCLUDING THE STEPS OF: PASSING RAW BLAST FURNACE GASES FROM THE TOP FURNACE AREA OF THE BLAST FURNACE TO THE LOWER CHAMBER TO PRESSURIZE SAID LOWER CHAMBER TO TOP FURNACE PRESSURE LEVEL TO EQUALIZE PRESSURE LEVELS IN THE LOWER CHAMBER AND THE TOP FURNACE AREA ACROSS THE LOWER MOVABLE BELL; PASSING RAW BLAST FURNACE GASES THROUGH A GAS CLEANER TO REMOVE SUSPENDED PARTICLES THEREFROM; AND PRESSURIZING SAID UPPER CHAMBER TO TOP FURNACE PRESSURE LEVEL TO EQUALIZE THE PRESSURES IN THE UPPER CHAMBER, LOWER CHAMBER AND TOP FURNACE AREA ACROSS THE LOWER 